Calling Javascript in an iOS web app from Objective-C

I am developing a web app that is being displayed in a UIWebView. The app is loaded locally, i.e, not from a web server. I am communicating from Javascript to ObjC via the shouldStartLoadWithRequest: method in the UIWebViewDelegate protocol.

The last thing I need is to be able to call Javascript functions from ObjC without any page reloads. I hope this is possible.